Computing devices such as personal computers, laptop computers, tablet computers, cellular phones, and countless types of Internet-capable devices are increasingly prevalent in numerous aspects of modern life. As computers become more advanced, augmented-reality devices, which blend computer-generated information with the user's perception of the physical world, are expected to become more prevalent.
To provide an augmented-reality experience, location and context-aware computing devices may be worn by a user as they go about various aspects of their everyday life. Such computing devices, which are commonly referred to as “head-mountable” computing devices, are configured to sense and analyze a user's environment and to provide information intelligently, as appropriate to the physical world being experienced by the user.